July 9th, 2015: For information on what's new in 1.3 RC 1, see the release announcement. For additional information about Android Studio, see the main developer site.
The release is available in the beta channel, so you can check for updates via Help > Check for Update... (on OSX, look in the Android Studio menu), and switch to the beta channel first if necessary. This will download and install a patch rather than download a full IDE image. Note however that for this build, the patches are quite large, since this build contains a lot of new code to support Android NDK development.
Mac: https://dl.google.com/dl/android/studio/ide-zips/126.96.36.199/android-studio-ide-141.2071668-mac.zip (348 MB)
Linux: https://dl.google.com/dl/android/studio/ide-zips/188.8.131.52/android-studio-ide-141.2071668-linux.zip (323 MB)